1 files changed, 13 insertions, 13 deletions

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index e1bf33018e6d..ba3440a45b6d 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -858,7 +858,7 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
 //	not know to synchronize with this RCU Tasks grace period) have
 //	completed exiting.  The synchronize_rcu() in rcu_tasks_postgp()
 //	will take care of any tasks stuck in the non-preemptible region
-//	of do_exit() following its call to exit_tasks_rcu_stop().
+//	of do_exit() following its call to exit_tasks_rcu_finish().
 // check_all_holdout_tasks(), repeatedly until holdout list is empty:
 //	Scans the holdout list, attempting to identify a quiescent state
 //	for each task on the list.  If there is a quiescent state, the
@@ -1220,7 +1220,7 @@ void exit_tasks_rcu_start(void)
  * Remove the task from the "yet another list" because do_exit() is now
  * non-preemptible, allowing synchronize_rcu() to wait beyond this point.
  */
-void exit_tasks_rcu_stop(void)
+void exit_tasks_rcu_finish(void)
 {
 	unsigned long flags;
 	struct rcu_tasks_percpu *rtpcp;
@@ -1231,22 +1231,12 @@ void exit_tasks_rcu_stop(void)
 	raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
 	list_del_init(&t->rcu_tasks_exit_list);
 	raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
-}
 
-/*
- * Contribute to protect against tasklist scan blind spot while the
- * task is exiting and may be removed from the tasklist. See
- * corresponding synchronize_srcu() for further details.
- */
-void exit_tasks_rcu_finish(void)
-{
-	exit_tasks_rcu_stop();
-	exit_tasks_rcu_finish_trace(current);
+	exit_tasks_rcu_finish_trace(t);
 }
 
 #else /* #ifdef CONFIG_TASKS_RCU */
 void exit_tasks_rcu_start(void) { }
-void exit_tasks_rcu_stop(void) { }
 void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
 #endif /* #else #ifdef CONFIG_TASKS_RCU */
 
@@ -1757,6 +1747,16 @@ static void rcu_tasks_trace_pregp_step(struct list_head *hop)
 	// allow safe access to the hop list.
 	for_each_online_cpu(cpu) {
 		rcu_read_lock();
+		// Note that cpu_curr_snapshot() picks up the target
+		// CPU's current task while its runqueue is locked with
+		// an smp_mb__after_spinlock().  This ensures that either
+		// the grace-period kthread will see that task's read-side
+		// critical section or the task will see the updater's pre-GP
+		// accesses.  The trailing smp_mb() in cpu_curr_snapshot()
+		// does not currently play a role other than simplify
+		// that function's ordering semantics.  If these simplified
+		// ordering semantics continue to be redundant, that smp_mb()
+		// might be removed.
 		t = cpu_curr_snapshot(cpu);
 		if (rcu_tasks_trace_pertask_prep(t, true))
 			trc_add_holdout(t, hop);